We just came back from our trip to Prague, Vienna and Budapest and had a wonderful time! We stayed three night in each and, with train travel, had two and a half days in each. We arrived in Prague in the afternoon and in our two and a half days there, we saw most of the city, which was absolutely beautiful! We did the Naked Tour Guide Early Morning Tour and really enjoyed it. The Charles bridge was not crowded and our tour guide, Simone, was so friendly and knowledgeable!
We left by train for Vienna and arrived mid-day. We took a day trip the next day to Melk and Durnstein, where we hiked the hillside to the castle ruins! It was one of my favorite days of our trip. We could have used another day in Vienna because of our day trip. There was much more we wanted to see.
Budapest was one of the most beautiful cities to see at night from the Danube. I highly recommend the Legenda candlelight dinner cruise! Food was very good but the scenery was gorgeous! In the two and a half days there, we saw a lot! You can always use another day in every city but we saw everything on our list! The Parliament tour was great but you need to get your tickets in advance and we found the House of Terror worth the wait to get inside.
Every one of these cities have excellent transportation so it is easy to get around (especially Budapest!) I hope your trip is as nice as ours! Three beautiful destinations!